1. Field of the Invention
The present invention relates to a technique for controlling pumping applications; and more particularly, the present invention relates to a method and apparatus for determining when there is no flow request in a pumping system using motor operation parameters, such as power current and torque, and controlling the controlling pumping applications based upon the determination.
2. Brief Description of Related Art
Recently, variable speed pump controls with energy saving and sensorless control means are known for hydronic pumping control applications, e.g., as disclosed in the patent applications set forth herein as references labeled [1] to [7] below. A sensorless converter, as shown schematically in FIG. 1, yields system pressure (ft) and flow rate values (GPM) providing motor power (current, or torque) and speed values, e.g., as disclosed in the patent applications set forth herein as references labeled [3-7] below. As one skilled in the art would appreciate, the sensorless converter would effectively be “senseless” without running the motor and obtaining motor values (e.g., RPM and hp) as input signals ready to be converted from otherwise. There would be no other pressure or flow value but zero which can be converted if the motor shuts off. No flow detection based upon the system pressure drop from the pump minimum pressure by a conventional no flow shutdown (NFSD) detection scheme is, therefore, unachievable, provided no additional no flow conditions or pump running states are introduced.
There is a need in the pump industry for a better way to determine no flow detection for sensorless pumping control applications.